From: Cong Wang <redacted>

When testing GRE tunnel, I got:

 # ip tunnel show
 get tunnel gre0 failed: Invalid argument
 get tunnel gre1 failed: Invalid argument

This is a regression introduced by commit c54419321455631079c7d
("GRE: Refactor GRE tunneling code.") because previously we
only check the parameters for SIOCADDTUNNEL and SIOCCHGTUNNEL,
after that commit, the check is moved for all commands.

So, just move it back inside SIOCADDTUNNEL and SIOCCHGTUNNEL.

After this patch I got:

 # ip tunnel show
 gre0: gre/ip  remote any  local any  ttl inherit  nopmtudisc
 gre1: gre/ip  remote 192.168.122.101  local 192.168.122.45  ttl inherit 

Cc: Pravin B Shelar <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <redacted>

---

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index c326e86..354d78c 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c

@@ -314,11 +314,6 @@ static int ipgre_tunnel_ioctl(struct net_device *dev,
 
 	if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
 		return -EFAULT;
-	if (p.iph.version != 4 || p.iph.protocol != IPPROTO_GRE ||
-	    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)) ||
-	    ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING))) {
-		return -EINVAL;
-	}
 	p.i_flags = gre_flags_to_tnl_flags(p.i_flags);
 	p.o_flags = gre_flags_to_tnl_flags(p.o_flags);